Since the introduction of mailer forms with U.S. Pat. No. 3,104,799, there have been a steady series of improvements. U.S. Pat. Nos. 3,339,827, 3,777,971 and 3,830,141 concerned increasing the freedom of the inside plies and means to control the position of the inside ply while inside the mailer to provide accurate registration of the computer printout.
U.S. Pat. No. 4,095,965 shows a mailer structure that best combines the various objectives in a mailer form, accurate position and control of the inside ply, minimum tenting, economical use of paper stock in manufacture and ease of opening the mailer and removal of the contents.
The difficulty of accomplishing these objectives in manufacturing is increased when length of the mailer is short. Mailers of 31/2 to 4" in length are particularly difficult. The size of the die cutting elements in order to be rigid enough to perform a reliable function limits the minimum length of the cut piece that can be given control after it is cut off. It is understandable that the longer the time and distance that the cut insert is without positive control, the less accurate will be its position inside the mailer and less reliable the production process.
The improvement of this invention is to cut the inside plies free only once each fold length. Typically 32/3 or 4" mailers are folded every 11 or 12" and 41/4" mailers every 81/2".
Consider the 41/4" size for example. The inside ply is typically cut to 31/2" long using a cutoff cylinder of 17 or 251/2" circumference. It can be seen that mechanical elements, rollers and such that can be fit in close enough to the cutoff cylinders to engage the 31/2" length before it is cut off and no longer controlled by the length of web feeding it into the cutting station would be so small as to lack the rigidity and strength necessary for reliable function in manufacture.
When these short lengths are handled in production according to this invention using the 41/4 length as an example, the inside plies would be cut from the infeeding web once every 81/2" with the inside plies having a length of 73/4". This is more than twice the length of a single inside ply.
A die cut chip is still removed between the two 41/4" portions of the inside plies so each portion can retain its ease of removal from the mailer but a portion (or portions) join the two 31/2" portions so that they can be handled for purposes of control in manufacturing as one piece. This method not only gives a much longer length with its easier control but also reduces the number of cut pieces by 1/2 (or 1/3) so there are fewer of these difficult pieces to be processed per 1000 forms lengths. This again improves manufacturing reliability.
By retaining the complete cutoff at each fold length, all of the tent reducing qualities of the mailer form are retained. The absence of a complete cutoff at the intermediate form length where the form is not to be folded does not increase tenting. Tenting is created only when the continuous form is folded causing some plies to fold along a longer path than others.